1. Field of the Invention
Embodiments of the invention generally relate to catwalks for conveying pipe to a drill floor from a lower section of a drilling rig or drill site. Specifically, embodiments of the invention relate to a hydraulic skate-cable drive system that is used instead of the chain and motor drive or winch system that are used by prior art catwalks.
2. Description of the Related Art
In a drilling operation or rig work-over operation, whether on a water-based or land-based drilling rig, pipe for the drilling operation, casing, or other tubulars are often stored at or supplied from a level that is lower than the drill floor. Operators typically use a “catwalk” to convey the pipe from the lower level to the drill floor. The pipe is typically mechanically transported (e.g. pushed with a skate and/or pulled in a v-shaped trough) from a level below the rig floor to the rig floor.
Prior art catwalks use a skate that is pulled from the lower end of the catwalk by a chain on a loop that is powered by a motor, or by a cable that is pulled toward the top of the catwalk trough using a winch. Such systems also require the use of a brake to stop the skate at a position where the skate causes the opposite end of the pipe or other tubular to be positioned near the drill floor where the rig workers can attach the end of the pipe to another hoist and move the pipe to the rotary or a setback area on the drill floor. The use of a motor and chain or a cable and winch along with a brake can lead to many mechanical breakdowns and to several potentially dangerous situations. If the chain breaks, the pipe and skate could move uncontrollably toward the bottom of the catwalk. If the brake fails, the pipe could be moved too far into the drill center, putting the drill floor workers at risk.
Accordingly, it would be useful to have a skate drive system that would prevent the skate and pipe from falling toward the bottom of the catwalk in the event of a system failure. It would also be useful to have a system that does not require the use of a brake to prevent the skate from moving too far up the trough so that the pipe does not put the rig workers at risk.